1. Speed, Distance, Time Calculations
Physical Science
8th Grade

2. The aim of this lesson is to be able to use the correct formulas to calculate speed, distance, or time

3. 15 mins = 0.25 hour 30 mins = 0.5 hour 45 mins = 0.75 hour
Reminder: How to change minutes into a decimal
15 mins = 0.25 hour
So: 3 hours 15 mins = 3.25 hours
30 mins = 0.5 hour
So: 7 hours 30 mins = 7.5 hours
45 mins = 0.75 hour
So: 2 hours 45 mins = 2.75 hours

4. The 3 formulas for Speed, Time & Distance:
Speed x
Time
Solving for Speed
Solving for Time
Solving for Distance D S T
Remember them from
this triangle:

5. Answer: His speed was 16 km / hr
A windsurfer travelled 28 km in 1 hour 45 mins.
Calculate his speed.
Distance
Time D S T
Speed =
28 km
1.75 hr =
1 hour 45 mins
= 16 km/hr
Answer: His speed was 16 km / hr

6. Answer: He travelled 125 km
A salesman travelled at an average speed of 50 km/h for 2 hours 30 mins. How far did he travel? D S T
Distance =
Speed x Time
= 50 km/hr x hr
2 hour 30 mins
= 125 km
Answer: He travelled 125 km

7. Answer: It took 9 hours 15 minutes
A train travelled 555 miles at an average speed of 60 mph. How long did the journey take? D S T
Distance
Speed
Time =
555 mi
60 mi/hr =
= hours
= 9 hours 15 mins
Answer: It took 9 hours 15 minutes